1. Field of the Invention
The invention relates in general to a power amplifier, and more particularly to a power amplifier which increases linearity.
2. Description of the Related Art
In a communication system, due to the difference in the modulation of signals, the required specifications of the required power amplifiers are also different. In recent years, the wireless communication network is conformed to IEEE 802.11a/b/g protocol, and since the orthogonal frequency-division multiplexing (OFDM) modulation used in the wireless communication network is similar to the amplitude modulation (AM), a power amplifier with higher linearity is thus required. In general, the power amplifier with high linearity increases the linearity through class A or class AB biasing, but the resulted power efficiency is lower. However, in order to further improve the communication quality, it is necessary to increase the linearity of the power amplifier.